The general objectives of this proposal are to examine the effects of exposure to abnormally high temperatures during the embryogeny of selected mosquitoes and to particularly elucidate the phenomenon of thermally induced unilateral or bilateral sterility that occurs in adults of both sexes of Aedes aegypti. Further, the effects thermally induced sterility have on mating competitiveness and ovipositions will be examined as well as a genetic analysis of any viable offspring produced by reciprocal crosses and out- crosses of unilaterally sterile individuals. With Aedes aegypti serving as a model system, two other members of the subgenus Stegomyia of medical importance will be subjected to thermal regimens to determine if a temperature and time period can be derived that will produce sterility as in the model. A complete morphologic examination of the reproductive tract will be made at the gross, histological and cytogenetic levels. The bionomics of laboratory populations of mosquitoes receiving calculated inputs of thermally stressed sterile individuals of one or both sexes will be examined to determine if these additions can successfully regulate a population. The information obtained could be used as a new approach to effect biological control singly or in conjunction with another factor of mosquito population control using Knipling's principle of applied sterile techniques. Populations sterilized during embryogeny could be easily distributed and manipulated for a more practical ecological method of mixture with feral individuals in the egg as well as the larval, pupal and adult stages of development. At no time during this investigation will chemical agents be used.